Internal combustion engines may experience an increase in temperature during combustion operation. To mitigate thermal degradation to the engine, cooling systems have been developed to cool components in the engine, such as the cylinder block and the cylinder head.
U.S. Pat. No. 4,377,990 discloses a water-cooled internal combustion engine with a cylinder head water jacket in fluidic communication with a cylinder block water jacket. A head gasket is disposed between the cylinder head and the cylinder block. The head gasket includes water galleries enabling coolant to flow through the gasket and between passages in the cylinder head and the cylinder block.
However, the inventors have recognized several drawbacks with cooling approaches such as the example above. For example, the location, size, and geometry of the water galleries in the head gasket may not provide sufficiently controlled cooling to certain sections of the cylinder head and the cylinder block, creating a potential for temperature above a desired operating value during engine operation. For example, the bridges between cylinders may experience less cooling than other areas of the cylinder block and the cylinder head, such as the exhaust manifold. As a result, uneven cooling in the cylinder block and/or cylinder head may lead to warping, cracking, as well as other types of thermal degradation. Furthermore, over-temperature conditions in some areas in the cylinders may decrease combustion efficiency and increase emissions. Further still, over-temperature conditions at bore bridge locations may increase head gasket degradation and top piston ring wear.
As such, in one approach an engine assembly is provided. The engine assembly includes a head gasket interposing a cylinder block and a cylinder head, the head gasket comprising a first layer in face sharing contact with a portion of a cylinder head attachment surface included in the cylinder block and having a first-layer coolant opening adjacent to two neighboring cylinders and a second layer having a second-layer coolant opening having a smaller cross-sectional area than the first-layer coolant opening.
In this way, the first-layer coolant opening may be sized and positioned to provide desired cooling to selected areas of the engine without necessarily compromising the structural integrity of the cylinder head and/or cylinder block through the addition of extra passages (although extra passages may be added, if desired). As a result in one embodiment, desired cooling may be provided to the bore bridge, enabling the bore bridge temperature to be maintained within limits during engine operation. Increasing the cross-sectional area of the first-layer coolant opening increases the amount of coolant that may be flowed near the cylinder block and specifically the bore bridge, thereby increasing the cooling provided to the bore bridge, if desired. Additionally, increasing the cross-sectional area of the first-layer coolant opening generates increased turbulence in the coolant flowing through the opening during some operating conditions. Therefore, the amount of heat that may be transferred to the coolant is increased. Additionally, increasing the cross-sectional area of the first-layer opening enables the coolant to travel across a greater amount of the cylinder block. Consequently, the thermal variability in the cylinder head and/or cylinder block may be decreased, thereby decreasing the likelihood of warping or other thermal degradation of the cylinder block and/or cylinder head.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.